Grub bird picked up after dropping pie (6)
I believe the answer is:
maggot
'grub bird' is the definition.
'maggot' can be an answer for 'grub' (thesaurus). I am not sure about the 'bird' bit.
'picked up after dropping pie' is the wordplay.
'picked up' becomes 'got'.
'after' is a charade indicator (letters next to each other).
'dropping pie' becomes 'mag' (I can't justify this - if you can you should believe this answer much more).
'got' after 'mag' is 'MAGGOT'.
(Other definitions for maggot that I've seen before include "immature flyer" , "one that may be in decay" , "youngster to fly" , "Larva of housefly or bluebottle" , "Larva often found in decaying matter" .)